The pressure of a solid is first of allthe first enemy of the builders. Because of the pressure of solids, it is impossible to implement some projects in principle. It is interesting that the ancients used this property on the contrary, creating majestic structures. Pyramids and many other architectural monuments - all these are the results of painstaking work in creating magnificent masters. Let us consider what is the pressure relative to solids.
The formula for the pressure of solids dating back to those times reads:
P = F / S,
those. the force acting on the surface is the pressure of the object.
It should be noted that in fact, the force of pressurebody is always positive and acts in both directions. Here the first law of Newton acts - the force of action is equal to the force of opposition. Applicable to life - the pressure that weighs the building will be the same for its lower layers and foundation. Therefore, the designers-builders always count on whether the foundation will sustain such a building. Of course, this calculation includes other factors (wind power - from the roof, groundwater, seismic activity, etc.).
Why is it necessary for a person to spread hisweight over a larger surface? And then remember the needle or knife. Both have an acute part, for better penetrating power. Now remember the skis and crawler tractors. Skiers do not fall into the snow, and tractors have good patency in the swamps, since they have a large contact area - for less submergence. This reflects the basic formula showing the pressure of solids - with the same force, but different areas, the pressure will be different. It will be inversely proportional to the area. Those. The larger the area, the greater the pressure. And vice versa.
Now back to the builders. Why do they have pressure - a big headache? It's all in the same square. After all, the stronger the material, the heavier it is. Remember the heavy concrete slabs-ceilings. Of course, in our time there are many durable and light materials. But even here it's not all that simple. Any construction project is estimated profitability. And if the price for such super-materials is high, then the estimate for construction will be large. As a result, either the customer does not pull finances, or the project will pay off for a very long time. But we already said above that the ancients used the pressure of solids to their advantage.
In those days, building materials were quiteLimited in assortment and in quantity. After all, there was no mining industry, and the stone was carved by hand. There were no connecting elements like concrete or mortar. It was necessary to use the pressure of solids instead of fixing. The fact is that the higher the pressure, the more strength is required from the materials. But on the other hand, this is also a great force of friction. And it, as is known, can have huge values. In the end, we get that the fasteners were not needed, everything was supported by gravity and frictional force.
Now imagine how much pressuretrain on the rails - 300,000 kPa !!! At the pressure of a specialized tracked tractor - 20 kPa. Quite an interesting moment, it would seem, a heavy swamp tractor, creates a relatively low pressure on the ground. This allows him to move around impenetrable and marshy areas at the expense of wide caterpillars. If we talk about the friction mentioned above, then it happens of different types and is determined by the formula:
F = μ × N, [H]
where F is the friction force [H],
μ is the coefficient of friction,
N is the normal reaction [H].
The force of pressure, as seen, has both positive,so is the negative point. Nature has adapted to this phenomenon. People from ingenious simple designs moved to the invention of new materials and technologies. Such a phenomenon exists in nature and must be taken into account.